What Throws Timing Off?
Thread Starter
Instructor
Joined: May 2010
Posts: 236
Likes: 0
From: Camden NY
St. Jude Donor '10
What Throws Timing Off?
Specs:
I had the spark plugs changed to AC Delco hot running gapped at .045 a few weeks ago. Ran great.
Then it started running rough at low end. Mechanic said the timing was off 30 degrees, reset it. It now runs like a new car through the entire range.
What could have made the timing go off that much? Does the MSD distributor have to be adjusted periodically?
I'm not a mechanic but trying to learn these things.
Thanks.
- 383 Stroker Engine installed May 2010
- Edelbrock 750 carb
- MSD HEI system 6A1 box
I had the spark plugs changed to AC Delco hot running gapped at .045 a few weeks ago. Ran great.
Then it started running rough at low end. Mechanic said the timing was off 30 degrees, reset it. It now runs like a new car through the entire range.
What could have made the timing go off that much? Does the MSD distributor have to be adjusted periodically?
I'm not a mechanic but trying to learn these things.
Thanks.
Burning Brakes
Joined: Oct 2001
Posts: 1,241
Likes: 4
From: Okinawa Okinawa
Unless the distributor was loose, I can't think of a reason it was 30 degrees off.
I'm not sure it would even run. That is like saying your at 14 degrees BTDC at idle and then you end up being 44 degrees?? Doesn't make sense.
I have been a few degrees off before and when I put it back to where it should be, the car runs much better. Especially down low.
I'm not sure it would even run. That is like saying your at 14 degrees BTDC at idle and then you end up being 44 degrees?? Doesn't make sense.
I have been a few degrees off before and when I put it back to where it should be, the car runs much better. Especially down low.
Le Mans Master
Joined: Feb 1999
Posts: 8,351
Likes: 75
From: Tampa Bay FL
Specs:
I had the spark plugs changed to AC Delco hot running gapped at .045 a few weeks ago. Ran great.
Then it started running rough at low end. Mechanic said the timing was off 30 degrees, reset it. It now runs like a new car through the entire range.
What could have made the timing go off that much? Does the MSD distributor have to be adjusted periodically?
I'm not a mechanic but trying to learn these things.
Thanks.
- 383 Stroker Engine installed May 2010
- Edelbrock 750 carb
- MSD HEI system 6A1 box
I had the spark plugs changed to AC Delco hot running gapped at .045 a few weeks ago. Ran great.
Then it started running rough at low end. Mechanic said the timing was off 30 degrees, reset it. It now runs like a new car through the entire range.
What could have made the timing go off that much? Does the MSD distributor have to be adjusted periodically?
I'm not a mechanic but trying to learn these things.
Thanks.
What did mechanic do to reset the timing? If he turned the distributor to reset, then it had to be loose to begin with.
Not that I am questioning your mechanic's integrity but there is little that can change other than the chain jumping/stretching or distributor turning.
Thread Starter
Instructor
Joined: May 2010
Posts: 236
Likes: 0
From: Camden NY
St. Jude Donor '10
Did same mechanic swap the plugs? Perhaps he loosened the distro' and it rotated a bit on its own.
What did mechanic do to reset the timing? If he turned the distributor to reset, then it had to be loose to begin with.
Not that I am questioning your mechanic's integrity but there is little that can change other than the chain jumping/stretching or distributor turning.
What did mechanic do to reset the timing? If he turned the distributor to reset, then it had to be loose to begin with.
Not that I am questioning your mechanic's integrity but there is little that can change other than the chain jumping/stretching or distributor turning.
2. He turned the distro to reset from what I remember.
3. I understand the mech integrity question. He's good and I take all my vehicles to him.
So, back to my other question re the MSD distro: can it get loose over time? I thought the HEI type distro was different than the standard old distros?
What can I do to prevent the above from happening in the future?
Thanks Ted and to all who replied.
Bob
Melting Slicks
Joined: May 2002
Posts: 2,716
Likes: 121
From: Sulphur LA
St. Jude Donor '05-'06,'11,'13-'14,'16,'18,'19,'24, '25
Verify the dist is seated correctly and that the hold down clamp is in the correct position and tightened down.
Verify timing to make sure its correct.
periodically check the timing to see if it changes, if it does the first thing to check is the dist to see if it has come loose and moved. If it has come loose you may need some form of thread locker on the dist hold down bolt.
It is possible they can come loose over time but I've not seen it as a common issue.
The MSD dist has the same clamp system as the HEI,
Neal
Verify timing to make sure its correct.
periodically check the timing to see if it changes, if it does the first thing to check is the dist to see if it has come loose and moved. If it has come loose you may need some form of thread locker on the dist hold down bolt.
It is possible they can come loose over time but I've not seen it as a common issue.
The MSD dist has the same clamp system as the HEI,
Neal
Tech Contributor
Joined: Aug 1999
Posts: 14,373
Likes: 6,371
From: At my Bar drinking and wrenching in Lafayette Colorado
On an HEI, the timing cannot change unless the distributor is physically rotated. If it is properly tightened down, the timing will never change. Either someone rotated your distributor, or it was never tightened properly.
On points-type distributors, timing would change with point rubbing block wear: As the block wore down, the dwell would change. And each degree of dwell changed the timing by the same degree. HEI eliminated the points, and thus eliminated any timing changes from wear of expendable parts. Other than the long-term effects of timing chain stretch, the timing will never change on an HEI or electronic ignition distributor.
Lars
On points-type distributors, timing would change with point rubbing block wear: As the block wore down, the dwell would change. And each degree of dwell changed the timing by the same degree. HEI eliminated the points, and thus eliminated any timing changes from wear of expendable parts. Other than the long-term effects of timing chain stretch, the timing will never change on an HEI or electronic ignition distributor.
Lars
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Instructor
Joined: Aug 2013
Posts: 105
Likes: 0
From: Lantana Florida
Specs:
I had the spark plugs changed to AC Delco hot running gapped at .045 a few weeks ago. Ran great.
Then it started running rough at low end. Mechanic said the timing was off 30 degrees, reset it. It now runs like a new car through the entire range.
What could have made the timing go off that much? Does the MSD distributor have to be adjusted periodically?
I'm not a mechanic but trying to learn these things.
Thanks.
- 383 Stroker Engine installed May 2010
- Edelbrock 750 carb
- MSD HEI system 6A1 box
I had the spark plugs changed to AC Delco hot running gapped at .045 a few weeks ago. Ran great.
Then it started running rough at low end. Mechanic said the timing was off 30 degrees, reset it. It now runs like a new car through the entire range.
What could have made the timing go off that much? Does the MSD distributor have to be adjusted periodically?
I'm not a mechanic but trying to learn these things.
Thanks.
It will turn on you and change when you go to read the timing.
Melting Slicks
Joined: Mar 2006
Posts: 3,456
Likes: 102
From: Piedmont Va
St. Jude Donor '11-'12-'13,'19-'20
Yup...Happened to me..original dampner took a spin after the rebuild to 383. 
Drifting
Joined: Aug 2010
Posts: 1,839
Likes: 45
From: nassau co. new york
this may be far fetched but is there a possibility you have a remote adjustable timing control box located somewhere,mine cannot be seen and is in the gas pedal area. it can tweak the timing by 7.5*.pn # 8680
Le Mans Master
Joined: Feb 1999
Posts: 8,351
Likes: 75
From: Tampa Bay FL
On an HEI, the timing cannot change unless the distributor is physically rotated. If it is properly tightened down, the timing will never change. Either someone rotated your distributor, or it was never tightened properly.
On points-type distributors, timing would change with point rubbing block wear: As the block wore down, the dwell would change. And each degree of dwell changed the timing by the same degree. HEI eliminated the points, and thus eliminated any timing changes from wear of expendable parts. Other than the long-term effects of timing chain stretch, the timing will never change on an HEI or electronic ignition distributor.
Lars
On points-type distributors, timing would change with point rubbing block wear: As the block wore down, the dwell would change. And each degree of dwell changed the timing by the same degree. HEI eliminated the points, and thus eliminated any timing changes from wear of expendable parts. Other than the long-term effects of timing chain stretch, the timing will never change on an HEI or electronic ignition distributor.
Lars
Le Mans Master
Joined: Nov 2006
Posts: 7,215
Likes: 1
From: Orlando FL
something doesn't make sense here. If the dist clamp is quality and is tight the timing will not move with MSD or HEI dist. Unless timing chain stretches (over time). If the hub on damper moved that would change the indications but the actual timing would not change.
My guess is that the dist clamp was loose
or the mechanic needed more gas money that day
Safety Car
Joined: Sep 2005
Posts: 4,213
Likes: 643
From: Orange County Ca
I had a mechanic do this while getting a smog check so that he could get more $$$ for a tune up.
He got pretty red in the face when I said--Oh look, the vac advance line at the dist fell off.
Drifting
Joined: Oct 2012
Posts: 1,524
Likes: 61
From: Medina Ohio